Hello @luuk ,
There is a way where you can set interactive messages such as instructions on the login screen where people can read and accept them before moving on to log in to the device. Every time the device restarts, an interactive banner will appear before the login window for all the users on the device. This can be achieved in both Windows and macOS devices. Remember that to achieve this you need access to an administrative account on the device.
For Windows devices, this can be achieved by editing the Group Policy Objects.
Search for Group Policy Editor using the start button and open it, navigate to Computer Configuration> Policies > Windows Settings > Security Settings > Local Policies, and select Security Options on the left pane.
Here you can find the policies “Interactive logon: Message text for users attempting to log on” and “Interactive logon: Message title for users attempting to log on”. These policies can be edited by right clicking on them and going to ’Properties’. These policies will set an instruction banner with a text message and a title respectively before the log in screen on Windows devices.
For macOS devices, this can be achieved by adding your instructions file to the ‘Security’ folder.
First, save your instructions file in a .txt, .rtf, or .rtfd file format under the name “PolicyBanner”.
Copy this PolicyBanner file to the /Library/Security/ folder.
For macOS devices, sometimes you might need to adjust permissions for the PolicyBanner file. This can be achieved by certain terminal commands.
For .txt or .rtf files, configure the permissions on the Policy Banner file to grant read privileges to Everyone (Other).
sudo chmod o+r /Library/Security/PolicyBanner.txt
sudo chmod o+r /Library/Security/PolicyBanner.rtf
For .rtfd files,
sudo chmod -R o+rx /Library/Security/PolicyBanner.rtfd
Also, updating the pre-boot volume can help in setting the changes in the boot environment.
diskutil apfs updatePreboot /
I hope this helps.
Have a great day.